Method of patterning magnetic products using chemical reaction

ABSTRACT

A method of patterning magnetic material includes forming a ferromagnetic material layer containing one element selected from the group consisting of Fe, Co and Ni on a substrate, selectively masking a surface of the ferromagnetic material layer, and making nonferromagnetic. The making nonferromagnetic step includes exposing an exposed portion in halogen-containing reaction gas, changing magnetism of the exposed portion and a lower layer thereof by chemical reaction, and making the exposed portion a nonferromagnetic material region. A magnetic recording medium is fabricated by using the magnetic material patterning method and includes a plurality of recording regions made of ferromagnetic materials, each containing at least one element selected from the group consisting of Fe, Co and Ni, and a nonferromagnetic material region for separating the recording regions from each other. The nonferromagnetic material region is a compound region of the ferromagnetic material and halogen.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Applications No. 2001-102215 filed onMar. 30, 2001 and No. 2001-399848 filed on Dec. 28, 2001, the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a high-density magneticrecording technology and, more particularly, to a method of patterningmagnetic products, magnetic recording media such as patterned mediaproduced by this method, and other magnetic products, and to a magneticrecording apparatus equipped with such magnetic recording media.

[0004] 2. Description of the Related Art

[0005] In recent years, because of an increase in a surface recordingdensity of a magnetic recording medium along with an increased recordingcapacity of a hard disk drive (referred to as HDD, hereinafter), eachrecording bit size on the magnetic recording medium has become extremelyminute, about several 10 nm. To obtain a reproducing output from such aminute recording bit, saturation magnetization and a film thickness aslarge as possible must be secured for each bit. However, the minuterecording bit reduces a quantity of magnetization per bit, and therearises a problem that is loss of magnetization information due tomagnetization reversal by “thermal fluctuation”.

[0006] Generally, it is said that this “thermal fluctuation” has alarger effect as a value of Ku·V/kT (Ku: a magnetic anisotropy constant,V: a minimum unit volume of magnetization, k: Boltzman's constant, T: anabsolute temperature) is smaller, and it is empirically said thatmagnetization reversal occurs because of “thermal fluctuation” atKu·V/kT<100.

[0007] In the case of a magnetic recording medium of a longitudinalmagnetic recording mode, since a demagnetization field becomes strong ina recording bit of a high recording density region, the medium tends tobe affected by “thermal fluctuation” even while a magnetic particle sizeis relatively large. On the other hand, in the case of a magneticrecording medium of a perpendicular magnetic recording mode, sincegrowth of a magnetic particle in a film thickness direction enlarges aminimum unit volume of magnetization V while keeping a particle size ofa medium surface small, the effect of “thermal fluctuation” can besuppressed. However, if a density of the HDD is increased much more inthe future, there may be a limit to resistance to thermal fluctuationeven for the perpendicular magnetic recording mode.

[0008] As a method for solving the problem of the thermal fluctuationresistance, a magnetic recording medium called “patterned medium”attracts attention. The patterned medium generally means a magneticrecording medium in which a plurality of magnetic material regions to berecording bit units are independently formed in a nonmagnetic materiallayer. In a general patterned medium, for the nonmagnetic materiallayer, for example, an oxide such as SiO₂, Al₂O₃ or TiO₂, a nitride suchas Si₃N₄, AlN or TiN, carbide such as TiC, and boride such as BN areused, and ferromagnetic material regions are selectively formed in thesenonmagnetic material layers.

[0009] In the patterned medium, since the ferromagnetic material regionswhich are the recording bit units are independent of each other,interference between the respective recording bits can be prevented.Therefore, the patterned medium is advantageous for reducing recordingloss and noises which are caused by adjacent bits. Moreover, patterningincreases resistance of domain wall movement (pinning effect of domainwall), making it possible to improve magnetic properties.

[0010] On the other hand, in the case of the HDD, positioning of amagnetic head in a target position (target track) on the magneticrecording medium or moving speed is controlled based on servoinformation pre-recorded on the magnetic recording medium. Generally,the servo information is recorded in each of servo regions (servosectors) radially provided at predetermined intervals in acircumferential direction on the magnetic recording medium.

[0011] Normally, writing of the servo information is carried out byusing a servo writing device called a servo track writer. Afterassembling the magnetic recording medium and the magnetic head into acasing of a HDD main body, the servo information is written. However, asa recording density of the HDD becomes much higher, the quantity of theservo information is increased proportionately thereto. Then, an area ofthe servo region on the magnetic recording medium is consequentlyincreased, reducing an area of an effective recording region (dataregion) in contradiction.

[0012] On the other hand, studies have recently been conducted on amagnetic recording medium structure of a “deep layer servo system” whichhas a servo region buried in a deep layer different from a magneticrecording layer. In this structure, since the recording region and theservo region can be formed by being laid on each other, a full surfaceof the magnetic recording medium can be used as the recording region,and the servo region can also be formed on the full surface of themagnetic recording medium. Thus, without sacrificing therecording-region, the magnetic head is enabled to perform highlyaccurate tracking at any point on the disk.

[0013] To fabricate the above-described patterned medium, it isnecessary to form fine magnetic material patterns in a large area. Onthe other hand, a magnetic random access memory (MRAM) has recentlyattracted attention as a new nonvolatile memory element. Manufacturingof the MRAM also necessitates highly integrated magnetic materialpatterning.

[0014] Conventionally, for such magnetic material patterning, thefollowing four processes have mainly been employed: first, a process forforming a magnetic material thin film to be fabricated; second, aphotolithography process for forming a resist film on the magneticmaterial thin film, and for forming a pattern on the resist film byusing photon energy, electron beams, ion beams or the like; third, aprocess for etching the magnetic material thin film using the resistpattern as a mask; and fourth, a process for removing remaining resistsor residuals left after the etching. Among the above processes, the thinfilm formation process, the photolithography process, and the residualremoval process can use methods applied in semiconductor processes.However, since the magnetic material is hard to be etched unlike ageneral semiconductor material, it is difficult to use normal reactiveion etching (RIE) used in a semiconductor process. Instead, therefore, aphysical etching method such as ion milling, in which field-acceleratedions sputter on a sample surface, has been used.

[0015]FIGS. 1A to 1E show a conventional method for manufacturing apatterned medium using ion beam milling. That is, as shown in FIG. 1A, aferromagnetic material layer 520 containing Fe, Co, Ni or the like isfirst formed on a substrate 510 of Si or the like by using a sputteringmethod or the like. Then, on this ferromagnetic material layer 520, aresist pattern 530 corresponding to a desired pattern is formed byelectron beam writing. Further, as shown in FIG. 1B, ion beam milling iscarried out by using this resist pattern 530 as a mask, and an exposedportion of the ferromagnetic material layer 520 is subjected to etching.Then, as shown in FIG. 1C, a remaining resist film is removed. As shownin FIG. 1D, a nonmagnetic material layer 540 is coated to fill groovesformed by the ion milling. Lastly, by subjecting the substrate surfaceto chemical mechanical polishing (CMP), a patterned medium shown in FIG.1E is obtained.

[0016] However, in the above-described conventional manufacturingmethod, since the ferromagnetic material layer 520 is fabricated usingthe ion beam milling, damage remains on a crystal structure of thefabricated surface. Thus, fabrication with no damage is desired tofurther improve magnetic properties.

[0017] In addition, as the etching by the ion milling is physical, thereis almost no difference in etching rates due to a difference betweenmaterials to be etched. As the ferromagnetic material layer 520 and theresist pattern 530 are scraped at approximately the same rate, an aspectratio of a shape that can be fabricated depends on a thickness of theresist pattern 530 as a mask. If there is about 20 nm difference inlevel between a surface of the resist pattern and the ferromagneticmaterial layer, a depth of 20 nm is a limit for a ferromagnetic materialto be etched. Thus, to carry, out fabrication of a good aspect ratio, athin resist cannot be used.

[0018] In the case of the high recording density HDD, a surface of themagnetic recording medium must be smooth to reduce spacing between themagnetic recording medium and the magnetic head. Accordingly, as shownin FIG. 1E, the nonmagnetic material layer 540 is buried in concaveportions of the etched ferromagnetic material layer 520, and then thesubstrate surface must be smoothed in a CMP step. This CMP step imposesa load on the process for forming the patterned medium.

[0019] On the other hand, a medium of a discrete tracking system (IEEETransactions on Magnetics Vol. 25, No. 5, P3381, 1989) has recently beenproposed as one type of a patterned medium. This patterned medium has amagnetic layer formed only in a track region. The magnetic layer isformed in a region between tracks using ion milling or the like.However, there is a level difference of 20 to 50 nm attributable topresence/non-presence of a magnetic layer on the medium surface, and thelevel difference causes a problem of considerably reducing seekingdurability.

[0020] In order to solve the problem of the level difference on themedium surface, a medium of a discrete system has been proposed, inwhich a magnetic layer that needs to become a region between tracks ismade nonmagnetic by implanting nitrogen ions or oxygen ions therein(Japanese Patent Laid-Open No. 5-205257(published in 1993)).

[0021] In addition, as a method for forming a patterned medium having asmoother surface, a method has been proposed for forming a patternedmedium by selectively oxidizing a medium surface using a mask (U.S. Pat.No. 6,168,845).

[0022] In the above-described method of implanting oxygen ions or methodof partially oxidizing the surface, since no etching steps are employed,the problem concerning the level difference on the surface due to ionmilling does not occur. However, these methods cannot completely removethe level difference on the medium surface. This is because a volume ofthe oxidized region made nonmagnetic is increased, and the mediumsurface of the oxidized region is raised.

[0023] In the case of using oxidation reaction, since a mask materialhaving high resistance to oxidation should preferably be used, a normalresist removing step such as an O₂ ashing process cannot be used toremove the mask material. Consequently, the removing the mask materialbrings a process load.

[0024] Also, regarding the manufacturing of MRAM, necessary filmsincluding a lower ferromagnetic material layer, a tunnel oxide filmlayer, an upper ferromagnetic material layer, and the like are formed ona substrate, and then these layers are physically etched using ionmilling when each memory element region is plotted. However,short-circuiting may occur between the upper and lower ferromagneticmaterial layers because of etching damage or etching residuals. Thus, itis desired to use a magnetic material patterning method having none ofthe above-described problems, high yields and good productivity.

[0025] On the other hand, the following problems exist concerningwriting in the servo region formed in the magnetic recording medium.First, when a normal sample servo (sector servo) system is used, a stepof writing servo information by using a conventional servo writer isnecessary. Since head movement is controlled and the servo informationis sequentially recorded in the respective servo regions of all tracksset on the magnetic recording medium, the step of writing servo trackinginformation is one of the steps that takes long time in themanufacturing process. In the future, a greater quantity of servoinformation will be necessary when a recording density is increased,requiring much longer time for the writing of the servo information bythe servo writer. Thus, in order to mass-produce high recording densityHDD devices inexpensively, it is required to shorten the time requiredfor the step of writing servo information.

[0026] Furthermore, even in the case of the magnetic recording mediumusing the deep layer servo system, a step of forming a deep layer servoregion is necessary in addition to the step of forming the magneticrecording medium. In the case of the deep layer servo system,especially, since writing of the servo information is carried out on thefull surface, a time load for the writing is extremely large, and thus arequest for shortening the time is stronger than that for the sampleservo system.

[0027] Therefore, also for the writing of the servo information, insteadof the method using the conventional servo track writer, it is desiredto employ a magnetic material patterning method having high productivityand capable of writing servo information in the magnetic recordingmedium all at once.

BRIEF SUMMARY OF THE INVENTION

[0028] An object of the present invention is to provide a magneticmaterial patterning method applicable to manufacturing of variousmagnetic products, which causes no physical damage and has highproductivity.

[0029] In order to achieve the above-described object, a first aspect ofthe present invention provides a method of patterning magnetic materialincluding preparing a ferromagnetic material layer containing at leastone element selected from the group consisting of Fe, Co and Ni,selectively masking a surface of the ferromagnetic material layer,exposing an exposed portion of the surface of the ferromagnetic materiallayer in halogen-containing active reaction gas or reaction liquid andconverting the exposed portion and a lower layer thereof into a compoundwith a component in the reaction gas or the reaction liquid by chemicalreaction to make the compound nonferromagnetic.

[0030] Here, “to make nonferromagnetic” means to lessen ferromagneticcharacteristics, and specifically means to convert a ferromagneticmaterial into a nonmagnetic or paramagnetic material.

[0031] According to the first aspect invention, since thenonferromagnetic material layer is selectively formed by the chemicalreaction between halogen and the ferromagnetic material layer, amagnetic pattern composed of ferromagnetic and nonferromagnetic materiallayers can be formed. Because of the use of the chemical reaction, nophysical damage is incurred, and also a large region can be patterned ina batch process. The halogenated nonferromagnetic material region haslittle volume expansion different from the case of oxidation, and thusan extremely smooth surface can be obtained without a step of polishingthe surface. Moreover, because of the use of halogenation reaction, ageneral resist can be used, and oxygen ashing process can be used forremoving the resist. By using this magnetic material patterning, it ispossible to manufacture patterned medium, to write servo information ina magnetic recording medium all at once, and to manufacture variousmagnetic products including a magnetic recording element such as anMRAM, and the like.

[0032] A second aspect of the present invention provides a magneticrecording medium including a plurality of recording regions made offerromagnetic materials, each containing at least one element selectedfrom the group consisting of Fe, Co and Ni, and a nonferromagneticmaterial region for separating the recording regions from each other,the region being a compound of the foregoing ferromagnetic material andhalogen.

[0033] According to the second aspect, a patterned medium is provided bythe recording region made of the ferromagnetic material and thenonferromagnetic material region made of the halogen compound of thisferromagnetic material. Since this nonferromagnetic material region isformed by the chemical method, the recording region is not damaged.Accordingly, manufacturing conditions cause no deterioration of magneticproperties, and good magnetic properties can be obtained. In addition,the surface of the nonferromagnetic material region and the recordingregion is not uneven, and a magnetic recording medium having highsubstrate smoothness can be provided.

[0034] A third aspect of the present invention provides a magneticrecording medium including a plurality of recording regions made offerromagnetic materials, each containing at least one element selectedfrom the group consisting of Fe, Co and Ni, and a servo layer forseparating the recording regions from each other, the servo layer havinga nonferromagnetic material region which is a compound of the foregoingferromagnetic material and halogen.

[0035] According to the third aspect, since servo information to bewritten in the servo layer of the magnetic recording medium is writtenbased on a pattern of presence/non-presence of a halogen compound layerwhich can be formed by chemical reaction. Therefore the servoinformation can be written in a large area all at once. Moreover, if theservo information is written based on the presence/non-presence of thehalogen compound layer, since volume expansion of the halogen compoundlayer is very small, a magnetic recording medium having excellentsmoothness of a substrate surface can be provided.

[0036] A fourth aspect of the present invention provides a magneticrandom access memory including; a lower electrode layer formed on asurface of a substrate; a first ferromagnetic material layer made of afirst ferromagnetic material containing at least one element selectedfrom the group consisting of Fe, Co and Ni, the first ferromagneticmaterial layer being formed on the foregoing lower electrode layer; atunnel insulating layer formed on the first ferromagnetic materiallayer; a second ferromagnetic material layer made of a secondferromagnetic material containing at least one element selected from thegroup consisting of Fe, Co and Ni, the second ferromagnetic materiallayer being formed on the tunnel insulating layer; and an insulatinglayer surrounding the foregoing first ferromagnetic material layer,tunnel insulating layer, and second ferromagnetic material layer, andcontaining a compound layer of the foregoing first ferromagneticmaterial and halogen, and a compound layer of the second ferromagneticmaterial layer and halogen.

[0037] According to the fourth aspect, the insulating layer surroundingthe first ferromagnetic material layer, the tunnel insulating layer, andthe second ferromagnetic material layer is formed of a halogen compoundlayer. Therefore element formation can be carried out by employing amagnetic material patterning method using halogenation reactionaccompanied with no etching. Thus, no leakage due to etching isincurred, and an MRAM having high integration can be provided in alarge-area batch process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]FIGS. 1A to 1E are process views showing a conventional patternedmedium fabrication method using ion milling.

[0039]FIGS. 2A and 2B are partial plan and perspective views showingpatterned media according to a first embodiment of the presentinvention.

[0040]FIGS. 3A to 3C are process views showing a manufacturing method ofthe patterned medium of the first embodiment of the present invention.

[0041]FIGS. 4A and 4B are views showing VSM data regarding aferromagnetic material layer and a nonferromagnetic material layeraccording to an example 1 of the first embodiment of the presentinvention.

[0042]FIGS. 5A and 5B are views showing a pattern of a resist maskaccording to an example 2 of the first embodiment of the presentinvention, and showing an electrophotograph of MFM image regarding anactually obtained patterned medium.

[0043]FIG. 6 is a sectional view showing a structure of a patternedmedium using a multilayer film according to a second embodiment of thepresent invention.

[0044]FIGS. 7A and 7B are plan views showing pattern examples of servoinformation.

[0045]FIG. 8 is a plan view showing a pattern example of a magneticrecording medium surface of a continuous servo system.

[0046]FIG. 9 is a sectional view showing a structure of a magneticrecording medium having a deep layer servo structure according to afourth embodiment of the present invention.

[0047]FIGS. 10A to 10E are process views showing a manufacturing methodof the magnetic recording medium having the deep layer servo structureof the fourth embodiment of the present invention.

[0048]FIG. 11 is a device perspective view showing a structure exampleof a hard disk drive according to a fifth embodiment of the presentinvention.

[0049]FIG. 12 is a device perspective view showing a structure ofanother hard disk drive according to the fifth embodiment of the presentinvention.

[0050]FIGS. 13A to 13C are process views showing a manufacturing methodof a MRAM according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] Description will be made of the embodiments of the presentinvention with reference to the accompanying drawings.

[0052] [First Embodiment]

[0053]FIG. 2A is a partial plan view showing a structure of a magneticrecording medium according to a first embodiment of the presentinvention; and FIG. 2B is a perspective view of the same.

[0054] The magnetic recording medium of the first embodiment of thepresent invention is a so-called patterned medium. As shown in FIGS. 2Aand 2B, this magnetic recording medium includes a recording layer 20 ona substrate 10. The recording layer 20 includes a ferromagnetic materialregion 20A and a nonferromagnetic material region 40. The ferromagneticmaterial region 20A contains any of Fe, Co and Ni, and has dottedexposed portions. The nonferromagnetic material region 40 surrounds atleast an upper layer portion of the ferromagnetic material region 20A.Substantial recording regions are separated from each other by thenonferromagnetic material region 40. Here, the nonferromagnetic regionmeans a region having lost magnetism at least as a ferromagneticmaterial, and exhibiting nonmagnetic, diamagnetic or paramagneticproperties.

[0055] The nonferromagnetic material region 40 is obtained by makingnonferromagnetic using chemically reacting a layer containing the samecomponent as that of the ferromagnetic material region 20A with activereaction gas. The composition of the nonferromagnetic material region 40is common to that of the ferromagnetic material region 20A. i.e.,containing one of Fe. Co and Ni.

[0056] According to such a magnetic recording medium of the firstembodiment, since an etching step such as ion milling needed in theconventional patterned medium fabrication process is not necessary, anda CMP step can be omitted, it is possible to greatly simplify a process.Moreover, since damage accompanied by the step of ion milling or thelike can be eliminated, it is possible to improve magnetic properties.

[0057] Next, the structure of the magnetic recording medium of the firstembodiment and its manufacturing method will be described more indetail.

[0058] As shown in FIG. 2A, the ferromagnetic material regions 20A areregularly disposed at constant intervals on the surface of the magneticrecording medium, and the nonferromagnetic material region 40 is formedto surround the ferromagnetic material regions. Each ferromagneticmaterial region 20A constitutes 1 recording bit as a recording unit.Preferably, each ferromagnetic material region 20A should be completelyindependent. However, as shown in FIG. 2B, it is satisfactory that atleast an upper layer portion of the ferromagnetic material region 20A issurrounded by the nonferromagnetic material region 40. Accordingly,recording regions are substantially separated from each other. Theferromagnetic material regions 20A should be set to 100 nm square orsmaller, preferably 80 nm square or smaller, in such a manner as to seta single magnetic domain state where respective directions ofmagnetization thereof are aligned in one direction. The shape of theferromagnetic material regions 20A are not limited to a rectangle, butvarious shapes can be employed, for example, a circle, an ellipticalshape and the like.

[0059] For a recording system of the ferromagnetic material region 20A,both longitudinal and perpendicular recording systems can be employed.To achieve a high recording density, how ever, the perpendicularrecording system is preferable.

[0060] The ferromagnetic material region 20A contains one of theelements Fe, Ni and Co, which are ferromagnetic materials, in itscomposition. For example, the ferromagnetic material region is composedof a crystal material of Ni—Fe or Fe—Al—Si: a Co-base amorphous materialof Co—Zr—Nb; an Fe-containing microcrystal material of Fe—Ta—N; Fe; Co;Fe—Co; Co—Cr; Ba ferrite; and the like. Among these, preferably, alloyof CoPt, CoCrPt, FeCo, FePd, FePt or the like having large perpendicularmagnetic anisotropy, or a material such as Co/Pd, or Co/Pt multiplayerfilm should be used for formation of the ferromagnetic material region.

[0061] The nonferromagnetic material region 40 is obtained byhalogenating a layer having an identical composition to that of theabove-described ferromagnetic material region 20A. For example, ashalogenated materials, CoF₂, CoF₃, FeF₂, FeF₃, and NiF₂ can be cited.These are all antiferromagnetic materials, but exhibit paramagnetism atroom temperature except for CoF₃ and FeF₃, because of low Neeltemperature (Tn).

[0062]FIGS. 3A to 3C are process views showing a manufacturing method ofthe magnetic recording medium of the embodiment.

[0063] First, as shown in FIG. 3A, a ferromagnetic material layer 20 isformed in a film thickness of, for example about 10 nm to 50 nm, on asubstrate 10 of Si or the like by a sputtering method or the like. Then,resist 30 is coated on the ferromagnetic material layer 20 by a spincoater or the like. There is no particular limitation on a filmthickness of the resist 30. The resist 30 may have a thickness to covera surface of the ferromagnetic material layer 20 without any pinholes.The resist 30 is selectively exposed by using EB writing system or thelike, and through a developing step, a resist pattern corresponding to aplane pattern of FIG. 2A is formed. That is, a surface of a portion tobe left as the ferromagnetic material region is covered with the resist30, and other portions are exposed. Then, the substrate obtained afterthe resist patterning are exposed to active reaction gas containinghalogen.

[0064] For the reaction gas containing halogen, for example, gas such asCF₄, CHF₃, CH₂F₂, C₂F₆, C₄F₈, SF₆, Cl₂, CCl₂F₂, CF₃l or C₂F₄ can beused.

[0065] The active reaction gas is preferably active radical. Variousmethods are available for generating radicals. For example, a existingplasma CVD apparatus or a dry etching apparatus can be used. Whenreaction gas is introduced into a chamber of such an apparatus and ahigh-frequency voltage is applied, field-accelerated electrons collidewith the reaction gas, the reaction gas is separated and radicals, whichare chemically extremely active, are generated. A substrate temperaturemay be set at normal temperature; however, to increase a reaction speedmore, heating may be applied within a range not affecting magnetism ofthe ferromagnetic material region.

[0066] A suitable example, of a plasma generation apparatus is, forexample, an inductive coupled plasma (ICP) apparatus. The ICP apparatusincludes a Platen RF having a function of inducting plasma to thesubstrate side, which is provided separately from a Coil RF mainlyhaving a function of generating plasma. These portions can be separatelyset for output thereof. For example, by setting the Coil RF to 300W andthe Platen RF to 0W, high density plasma, which is suitable forproducing radical reaction, is generated. An effect of sputtering can besuppressed to a minimum since no damage is given to the medium surface.To prevent sputtering the medium surface, a pressure in a reactionchamber should be set slightly high, e.g., 10 to 30 mtorr, morepreferably about 20 mtorr. In the case of using CF₄ as reaction gas, agas flow rate should be set in a range of 10 to 50 sccm, preferablyabout 20 sccm.

[0067] For example, as shown in FIG. 3A, when the ferromagnetic materiallayer 20 not covered with the resist 30 is exposed to active fluorine(F) radicals generated from CF₄ gas, the exposed surface of theferromagnetic material layer 20 is gradually halogenated in a depthdirection by the F radicals.

[0068] Thus, as shown in FIG. 3B, the halogenated region becomes ahalide layer, and becomes a nonferromagnetic material region 40 whichhas lost magnetism. On the other hand, the region having its surfacecovered with the resist 30 becomes a ferromagnetic material region 20A.A depth of the nonferromagnetic material region 40 should preferably beset approximately equal to a depth of the ferromagnetic material layer20. However, such equality of depth is not always necessary, and withrespect to a thickness of the ferromagnetic material layer 20, forexample, the depth of the nonferromagnetic material region 40 is set to½ of the ferromagnetic material layer 20 or more, more preferably ⅔thereof or more.

[0069] Note that a dry process is not always necessary, and a similarresult can be obtained by a wet process. For example, CoCl₃ or the likemay be halogenated by using a HCl solution.

[0070] Lastly, by removing the remaining resist 30, a patterned mediumshown in each of FIG. 3C and FIGS. 2A and 2B can be obtained. For theremoval of the resist, ashing process using oxygen plasma can beemployed.

[0071] According to the manufacturing method of the above-describedfirst embodiment, it is possible to obtain a patterned medium in whichthe recording region of the ferromagnetic material layer 20A issurrounded with the nonferromagnetic material region 40 which ishalogenated metal. For example, since Neel temperatures (Tn) of CoF2 andNiF2 which are the nonferromagnetic material region 40 obtained byhalogenation reaction are very low, respectively 38K and 73K. Thus, asCoF2 and NiF2 surely exhibit paramagnetism at room temperature, nomutual magnetic operation occurs between adjacent recording bits, andadjacent magnetic recording is isolated. Therefore, this manufacturingmethod using halogenation reaction is suitable for manufacturing thepatterned medium.

[0072] On the other hand, for CoO and NiO obtained by oxidationreaction, which are the nonferromagnetic material regions of thediscrete medium and the patterned medium disclosed in Japanese PatentLaid-Open No. 5-205157 (published in 1993) and U.S. Pat. No. 6,169.845already described above, magnetic phase transition temperatures (Tn) arerespectively 291K and 548K. Thus, oxidized metal generated by oxidationreaction exhibits antiferromagnetism at room temperature. In the case ofa medium including a ferromagnetic material buried in a diamagneticmaterial, a ferromagnetic material layer is magnetically not completelyisolated, and thus magnetic recording of an adjacent recording bit maybe adversely affected. For example, when identical signals are recordedin adjacent bits, there is a high possibility that magnetizationreversal will extinguish a stored content.

[0073] Therefore, the patterned medium having the nonmagnetic materialregion obtained by the halogenation reaction according to the firstembodiment can acquire better magnetic properties compared with thepatterned medium having the nonmagnetic material region obtained by theoxidation reaction.

[0074] Generally, since a halide, especially a fluoride has strong ioncrystallization as represented by CaF₂ (fluorite), it is easy to obtaina crystal of good orientation. The crystal is unlikely to be dissolvedin water, and is chemically stable. When a fluoride and an oxide of thesame metal are compared with each other, bond dissociation energy (D) ofthe fluoride is generally larger. For example, D of MgF₂ is 511.7kJ/mol, and D of MgO is 336.8 kJ/mol. Thus, the fluoride can be expectedto exhibit higher stability than the oxide.

[0075] Moreover, the good orientation of the fluoride may realize auniform particle size of the adjacent ferromagnetic material regions20A, and thus an effect of more improvement in the magnetic propertiesof the ferromagnetic material region can be expected.

[0076] In addition, CoO which is an oxide is tetragonal where a latticeconstant of a c axis is 4.124. However, since a lattice constant of a caxis of a fluoride CoF₂ is small, i.e., 3.180, there is almost littlevolume expansion such as that in the oxidation reaction occurs.Therefore, unevenness due to the presence of a halogenated region doesnot generated, providing extremely good smoothness.

[0077] According to the manufacturing method of the above-describedfirst embodiment, since the surface of the ferromagnetic material layer20 is not etched, surface heights of the nonferromagnetic materialregion 40 and the ferromagnetic material region 20A are approximatelyequal to each other, making it possible to approximately maintain smoothsurfaces of reaction starting time. Thus, unlike the conventional caseof fabricating a patterned medium by using ion milling, a step ofsmoothing a surface by CMP is not necessary in the last step of theprocess. Therefore, it is possible to greatly shorten the manufacturingprocess.

[0078] In addition, in the case of using ion milling, an influence ofdamage caused by the ion milling remains in a fabricated surface layerof the ferromagnetic material region, for example its sidewall. However,according to the method of the above-described first embodiment, theferromagnetic material region 20A is not damaged. Thus, characteristicdeterioration caused by the process is unlikely to occur in theferromagnetic material region 20A.

[0079] Moreover, in the above-described conventional patterning methodusing the oxidation reaction, since metal such as Ti having highresistance to oxidation or an inorganic film such as SiO₂ is mainly usedas a mask, a RIE process must be executed to remove such a mask afteroxidation reaction. During this RIE process, the medium surface may bepartially damaged by sputtering. On the other hand, in the method ofpatterning a magnetic material according to the first embodiment, sincethe halogenation reaction is used, a general resist mask can be used.The resist can be easily removed by oxygen ashing process which canreduce the damage to the medium surface to a minimum.

[0080] Moreover, according to the manufacturing method of theabove-described first embodiment, because the shape of the ferromagneticmaterial region 20A is not dependent on a resist film thickness, theresist film thickness can be reduced. Thus, for example, it is possibleto use a thin resist pattern having a dot thickness of about 20 nmutilizing a self-organization phenomenon (phase separation phenomenon)of a diblock copolymer. A block copolymer means a copolymer composed ofa linear polymer including a plurality of homopolymers as constituentcomponents. Especially one obtained by chemically coupling two kinds ofpolymers is called a diblock copolymer. For example, for such a resistmaterial, a diblock copolymer composed of polystyrene (PS) andpolymethyl methacrylate (PMMA) generally used for an optical disksubstrate or the like can be used.

[0081] By controlling a composition ratio and a molecular weight of theblock copolymer, various structures can be easily formed. For example,when a solution in which polystyrene (PS) and polymethyl methacrylate(PMMA) are mixed is coated on the ferromagnetic material layer 20, asea-island (Sphore) structure can be obtained, which is phase-separatedinto an “island” region of PMMA and a “sea” region of PS. By exposingthis sea-island structure to ozone and by selectively vaporizing PMMAtherein, dot patterns each having a regular PMMA thickness of 20 nm anda diameter less than 40 nm can be obtained. That is, dot patterns of asize suited for formation of a patterned medium can be formed all atonce.

[0082] In the conventional method of using the ion beam milling, use ofthe above-described thin resist is difficult. However, according to themethod of the first embodiment using the chemical method, such thinresist can be used as an etching mask. If patterned- resist is obtainedby utilizing the self-organization phenomenon of the diblock copolymer,the patterning of the resist by EB writing system which takes long timeis made unnecessary. Thus, the method of the embodiment becomes veryeffective means for simplifying the process.

[0083] As described above, according to the magnetic recording medium ofthe first embodiment, in addition to excellent resistance to thermalfluctuation and the effect of preventing crosstalk and partial erasingfrom an adjacent bit, which the patterned medium structure itself has,it is possible to improve magnetic properties by reducing damagereceived in the manufacturing process, and to shorten the process.

[0084] Hereinafter, description will be made for examples of examinationthat the inventors made in order to verify the effect of the patternedmedium of the first embodiment.

[0085] (Example 1) First, CoPt was deposited by 20 nm on a Si substrateby a sputtering method, and a magnetic force microscope (MFM) image on asurface of this sample was observed. An image of a perpendicularmagnetic recording medium having a high-contrast maze pattern which is atypical ferromagnetic pattern was observed. A hysteresis curve in aperpendicular direction was measured by a vibrating sample magnetometer(VSM), and a curve, as shown in FIG. 4A, which has a squareness ratio of0.49 and a coercive force of 1500 Oe was obtained.

[0086] Then, a composition of the sample surface was analyzed by usingX-ray photoelectron spectroscopy (XPS). A peak inherent in Co wasobserved at binding energy=778 eV. A peak (781 eV) of CoO wassimultaneously observed; however, this peak was due to natural oxidationof oxygen in the atmosphere. Two peaks inherent in Pt were also observedwithin the range from 70 to 75 eV.

[0087] Subsequently, CoPt was deposited by 20 nm on the Si substrate bythe sputtering method. This sample was placed in a sealed chamber,plasma was generated in the chamber, and CF4 gas was introduced togenerate F radicals. Then, a surface of the sample was exposed to the Fradicals for about 30 seconds. A sample temperature in this event wasset to room temperature.

[0088] Then, when a composition of the sample surface was analyzed byusing XPS, both peaks 778 eV(Co) and 781 eV(CoO) disappeared, and a newpeak (cobalt fluoride) of 783 eV was observed. No peak shifting wasobserved at a Pt peak. This shows that exposure to the F radicals surelyconverted the surface into cobalt fluoride.

[0089] In addition, when the composition of the sample surface wasanalyzed by using scanning Auger electron spectroscopy (AES), conversionof CoPt into cobalt fluoride was verified. By observing changes of peaksof the cobalt fluoride with passage of time while sputtering, it wasfound out that the cobalt fluoride existed from a medium surface to adepth of about 10 nm. It was also verified that it was possible tocovert all 20 nm which is a thickness of CoPt into a halide by extendingthe exposure time of the F radicals.

[0090] When a MFM image of the sample surface was also observed, atypical MFM image seen when magnetization disappeared was observed.

[0091] By observing this sample with VSM, data of a typical paramagneticmaterial as shown in FIG. 4B was obtained. This is attributed to thefact that CoF₂ is originally an antiferromagnetic material, but behaveslike a paramagnetic material at room temperature because of an extremelylow Neel temperature.

[0092] As a result, it was verified that the CoPt film which is aferromagnetic material layer was converted into a halide within a shorttime by being exposed to the F radicals, and that magnetism thereofdisappeared.

[0093] (Example 2)

[0094] A patterned medium sample, in which ferromagnetic material CoPtregions are surrounded by antiferromagnetic material CoF₂, was prepared.That is, first, CoPt was deposited by 20 nm on a Si substrate by asputtering method. Then, resist was coated in a thickness of about 1.0μm on this CoPt film by spin coating, and a resist pattern as shown inFIG. 5A was formed after batch exposure and development. In thisexample, a size of each ferromagnetic material region on a surface layerwas set to 2.0 μm square.

[0095] A surface of this sample was exposed in F radicals generatedunder conditions similar to those of the example 1 for about 30 secondswhile being maintained at room temperature. Then, the resist was removedby using an oxygen ashing apparatus.

[0096] When a MFM image of this sample was observed, a magnetic patternequivalent to a resist pattern as shown in FIG. 5B was obtained. Thatis, regarding a region covered with a resist film, a MFM image of aferromagnetic material having typical perpendicular magnetic anisotropywas observed. In a region where a CoPt surface was exposed, a typicalMFM image seen when magnetization disappeared was observed.

[0097] Moreover, when the region where the CoPt surface was exposed wasanalyzed by using XPS, conversion of CoPt into a halide was verified.Identification of a composition was carried out by using XPS, however,verification can be carried out by using a surface analyzer such as AESor secondary ionization mass spectrometry (SIMS).

[0098] The sample thus obtained was a uniformly continuous thin filmhaving no unevenness on its surface. In addition, magnetically, as shownin FIG. 2A or FIG. 2B, the sample was verified to be a patterned mediumwhere ferromagnetic material regions 20A isolated at least on a surfacelayer were regularly arrayed in a nonferromagnetic material region 40.

[0099] (Example 3)

[0100] In order to form finer patterns of the ferromagnetic materialregion than that of the above-described example 2, electron beam (EB)writing was carried out in exposure of resist. Accordingly, fineferromagnetic material region patterns of about 80 nm square wereformed. Other conditions were the same as those of the above example 2,and by using these conditions, a sample was prepared. That is, CoPt wasdeposited by 20 nm on a Si substrate by sputtering. Then, nega-resistwas coated thereon, a minute resist pattern was formed by EB writing,and exposure thereof in F radicals was carried out for about 30 secondsat room temperature. Thereafter, the resist was removed.

[0101] An obtained sample was observed by MFM, and a single color imagewas obtained in a ferromagnetic material region. That is, it wasverified that by reducing the ferromagnetic material region to a size ofabout 80 nm square, a single magnetic domain state was set in thisregion. When magnetic properties in a perpendicular direction wereobserved by VSM, a squareness ratio of 1.00 and a coercive force of 4500Oe were obtained. These values represent a squareness ratio twice aslarge and a coercive force three times as large compared with the VSMcurve of the CoPt film not exposed in the F radicals after sputtering inthe example 1, and improvement in the magnetic properties was observed.It was also verified that in a comparative example 1 to be describedlater, better magnetic properties were obtained compared with apatterned medium of an equal size fabricated by the conventional method.

[0102] (Example 4)

[0103] CoPt was deposited by 30 nm on a Si substrate by sputtering.Then, the resultant structure was left under oxygen atmosphere for oneday to oxidize a CoPt surface. When the surface was observed by XPS, apeak (781 eV) of CoO was verified.

[0104] Subsequently, resist was coated in a thickness of about 1.0 μm onthe CoPt film by spin coating, and after batch exposure and development,a plurality of rectangular resist patterns of 2.0 μm square as shown inFIG. 5A were formed.

[0105] A surface of this sample was exposed in F radicals generatedunder similar conditions to those of the example 1 for about 30 secondswhile being maintained at room temperature. Then, the resist was removedby using an oxygen ashing apparatus.

[0106] When a MFM image of this sample was observed, a magnetic patternequivalent to a resist pattern as shown in FIG. 5B was obtained. Thatis, regarding a region covered with the resist film, a MFM image of aferromagnetic material having typical perpendicular magnetic anisotropywas observed. In a region where a CoPt surface was exopsed, a typicalMFM image seen when magnetization disappeared was observed. In asimultaneously observed surface leveling image (similar to AFM surfacetopological image), almost unevenness is not observed.

[0107] In addition, the region where the CoPt surface was exposed wasanalyzed by using XPS, conversion of CoPt into a halide was verified.

[0108] As a result, it was found out that even when a reacting surfacewas naturally oxidized beforehand, a halide layer could be obtained bylater substitution reaction of a fluorine radical. It was also verifiedthat this method enabled formation of a patterned medium having almostflat medium surface.

[0109] (Comparative example 1)

[0110] As a comparative example, a sample was prepared according to aconventional manufacturing method of a general patterned medium. Thatis, CoPt was deposited by 20 nm on a Si substrate by a sputteringmethod. Then, nega-resist was coated on a surface thereof, and by EBwriting, a pattern equivalent to a ferromagnetic material region of 80nm square was formed similarly to the example 3. Subsequently, a surfaceof the sample was uniformly etched by Ar ion beam milling. When CoPt ofa region not covered with the resist was etched by about 20 nm, theremaining resist was removed by O₂ ashing. Then, SiO₂ was deposited by20 nm by sputtering, and the surface was covered so as to fill a CoPtgroove portion formed by ion milling. In addition, the surface waspolished by CMP processing. Accordingly, a patterned medium in whichCoPt ferromagnetic material regions of about 80 nm square, which areindependent of one another, are surrounded with SiO₂ was obtained. Thatis, the prepared sample was equivalent to one where the halide portionof the sample prepared in the example 3 was changed to SiO₂.

[0111] When a CoPt portion was observed by MFM, an image wasapproximately the same as the magnetic image of the example 2 having thesize of the ferromagnetic material region set to 2 μm square. Whenmagnetic properties in a perpendicular direction were observed by VSM, asquareness ratio of 0.70 and a coercive force of 2000 Oe were obtained.These values represented improvement in magnetic properties comparedwith those of the CoPt continuous film not exposed to the F radicalsimmediately after sputtering in the example 1. However., compared withthe patterned medium having the ferromagnetic material region of thesame size as the example 3, the magnetic properties were inferior.

[0112] (Result)

[0113] By comparing the comparative example with the example 3, it wasverified that the manufacturing process of the patterned medium of theexample 3 was not only simple, but also the magnetic properties of theferromagnetic material region thereof were improved compared with thoseof the patterned medium of the comparative example.

[0114] One of the reasons may be as follows. That is, in the case of thesample of the comparative example, since fabrication is carried out byusing the ion beam milling, the fabricated surface of the ferromagneticmaterial region was at least damaged. On the other hand, in the case ofthe sample of the example 3, since the chemical method accompanied withno physical damage is used, there is no damage on the surface of theferromagnetic material.

[0115] In addition, in the case of the patterned medium of the example3, CoPt is converted into a halide to form the nonferromagnetic materialregion. However, the halide is an ionic crystal, and is not amorphoussuch as SiO₂ forming the nonferromagnetic material region of thepatterned medium of the comparative example. Thus, it can be conceivedthat good orientation of the ionic crystal realizes a uniform CoPtparticle size of the adjacent ferromagnetic material regions, improvingmagnetic properties more.

[0116] Moreover, from the result of the example 4, it was verified thatwhen halogenation reaction was used for formation of the nonmagneticmaterial region, surface smoothness required for the HDD medium, i.e., adifference in level of 0.8 nm or lower, was sufficiently obtained.

[0117] [Second Embodiment]

[0118]FIG. 6 is a sectional view showing a structure of a patternedmedium according to a second embodiment.

[0119] Also in the patterned medium of the second embodiment, a methodfor forming a nonferromagnetic material region uses the similar chemicalmethod as that described in the first embodiment. A difference from thefirst embodiment is that a multilayer film is formed instead of theferromagnetic material thin film formed on the Si substrate. Themultilayer film includes a plurality of layers, e.g., ferromagnetic andmetal layers, alternately laminated in a regular manner. For example, amultilayer film obtained by alternately laminating Co and Pt or Co andPd is known. By using such a multilayer film a high coercive force canbe obtained. Other constitutions and manufacturing methods are common tothose of the first embodiment.

[0120] In order to form the patterned medium of the second embodiment,first, as shown in FIG. 6, a multilayer film 21 alternately laminatingCo layers 21 a and Pt layers 21 b is formed on a substrate 10 by asputtering method or the like. For example, a film thickness of the Colayer 21 a should be set in a range from 0.2nm to 1.0 nm, preferably 0.5nm. A film thickness of the Pt layer 21 b should be set in a-range from0.5 nm to 2.0 nm, preferably 1.0 to 2.0 nm. The number of the respectivelayers is about 10; the number of the Pt layers is larger than that ofthe Co layers by one layer.

[0121] The process thereafter is basically similar to that of the firstembodiment. Resist is coated on the multilayer film 21, the resist isselectively exposed by using EB writing or the like and is developed,then a resist pattern equivalent to a portion to be left as aferromagnetic material region is formed. Subsequently, a surface of themultilayer film 21 having the resist pattern formed thereon is exposedin active reaction gas or in a reaction liquid.

[0122] For example, when the surface of the multilayer film 21 havingthe resist pattern formed thereon is exposed to F radicals, the Fradicals halogenate the exposed surface of the multilayer film 21 toform a halide region 25.

[0123] For an artificial lattice, a regularly laminated structure,especially its interface, is important. Accordingly, if even one layerof the laminated structure is physically damaged or a chemicalcomposition thereof is changed, magnetism in upper and lower laminatedportions is lost. Thus, as shown in FIG. 6, the halide region 25 may beformed only on a limited surface layer film of the multilayer film 21.

[0124] Thereafter, by removing the remaining resist, as in the caseshown in FIG. 2A, a patterned medium including a ferromagnetic materialregion 20A made of the multilayer film and a nonferromagnetic materialregion 40 surrounding the ferromagnetic material region 20A can beobtained.

[0125] As described above, in the conventional method using the ion beammilling, since the fabricated surface of the ferromagnetic materialregion is damaged, it is difficult to form a patterned medium using amultiplayer film, in which even small damage affects magneticproperties. However, by using the method of the second embodiment, thepatterned medium using the multilayer film can be fabricated easily.

[0126] Also in this case, as described above in the first embodiment, athin resist film can be used. Thus, instead of resist patterning carriedout by using EB writing, it is possible to use a resist patterningmethod using a self-organization phenomenon of a diblock copolymer.

[0127] Hereinafter, description will be made for examples of examinationthat the inventors made in order to verify an effect of the patternedmedium using the multilayer film of the second embodiment.

[0128] (Example 5)

[0129] First, Co films in a thickness of 4.4 nm and Pt films in athickness of 9.5 were alternately laminated to form ten layers on a Sisubstrate by a sputtering method, thus forming a multilayer film In thisstate, MFM was observed, and a magnetic pattern inherent in aferromagnetic material having perpendicular magnetic anisotropy wasidentified. In addition, when magnetic properties in a perpendiculardirection were observed by VSM, a squareness ratio of 0.8 and a coerciveforce of 2000 Oe were obtained.

[0130] Subsequently, resist was coated in a thickness of 1.0 μm on themultilayer film and a fine ferromagnetic material region pattern ofabout 80 nm square was formed by EB writing. Under conditions similar tothose of the example 1, this multilayer film with the resist pattern wasexposed to F radicals for about 30 seconds at room temperature, and asurface of an exposed portion was halogenated. Then, the remainingresist was removed.

[0131] Observation was made for a MFM image of a sample thus obtained,and presence of a ferromagnetic material region and a nonferromagneticmaterial region at a high contrast ratio was verified. This contrastratio was higher than that obtained in the example 3. For theferromagnetic material region, it was also verified that a single colorimage was formed, and a single magnetic domain was formed. For thisportion, magnetic properties in a perpendicular direction were observed,and a squareness ratio of 1.00 and a coercive force of 5000 Oe wereobtained.

[0132] It was thus verified that when a patterned medium using such amultilayer film was formed, an S/N ration higher than that in the caseof using a single CoPt layer film was obtained.

[0133] (Example 6)

[0134] Under conditions similar to those of the example 5, a multilayerfilm was formed on a substrate. On the multilayer film a solution ofPS-PMMA diblock copolymer was coated, and a sea-island structure whichis phase-separated into an “island” region of PS and a “sea” region ofPMMA was formed. This sea-island structure was exposed in ozone, PMMAwas selectively vaporized, and dot patterns of PS were formed in athickness of about 20 nm and a diameter of about 40 nm.

[0135] Subsequently, this sample was exposed to F radicals at roomtemperature for about 30 seconds, and a surface of the exposed portionwas halogenated. Then, the remaining PS was removed.

[0136] A MFM image of the obtained sample was observed, and it wasverified that a region covered with PS formed a ferromagnetic materialregion of a single magnetic domain, and regions other than the aboveregion became nonferromagnetic material regions.

[0137] As described above, it was verified that according to the methodof the embodiment, it was possible to fabricate a patterned mediumhaving a fine ferromagnetic region by employing a resist pattern usingthe self-organization phenomenon of the diblock copolymer with a leveldifference of only 20 nm.

[0138] In other words, instead of EB writing which takes long time, byusing a patterning method of resist using phase separation of a diblockcopolymer, it is possible to greatly shorten a resist patterningprocess.

[0139] [Third Embodiment]

[0140] A third embodiment relates to writing of servo information in aservo region on a magnetic recording medium. The magnetic materialpatterning method using the halogenation reaction described in the firstembodiment can be used not only for forming a patterned medium but alsofor writing servo information in the servo region all at once.

[0141] That is, in the magnetic recording medium of the thirdembodiment, resist is coated on a surface of a recording layer having aferromagnetic material layer formed thereon, and an opening patternequivalent to a servo signal pattern is formed in a portion to be aservo region. As the servo signal pattern, one generally used may beused. For example, formed is one as shown in FIG. 7A in which aplurality of wedge-shaped patterns 65 are arrayed, or one as shown inFIG. 7B in which patterns 66 alternately formed left and right arearrayed in two rows by being shifted up and down by half pitches.

[0142] After the resist pattern is formed, under conditions similar tothose of the first embodiment, the magnetic recording medium is exposedin active reaction gas, for example F radicals. A ferromagnetic materiallayer of the opening portion of the resist pattern is halogenated to bechanged to a nonferromagnetic material region. By removing the resist, amagnetic pattern equivalent to the resist pattern can be formed in theservo region on the magnetic recording medium.

[0143] As long as the magnetic pattern formed in the servo region can beverified as magnetic information, it is not a problem that which one ofinner and outer sides of the pattern should be set as a ferromagneticmaterial region or as a nonferromagnetic material region.

[0144] By using the above method to write the servo information, writingoperations in the respective regions can be carried out in a batchprocess. Thus, it is possible to greatly shorten time necessary forwriting of the servo information.

[0145] Moreover, the method of writing servo information according tothe third embodiment can also be applied to writing servo information ofa magnetic recording medium of a continuous servo system, which iscapable of always taking out a servo signal in any position of amagnetic head on a disk. As the magnetic recording medium of-thecontinuous servo system, for example, a magnetic recording medium isdisclosed in Japanese Patent Laid-Open No. 2000-19200 (published in2000). This magnetic recording medium includes servo patterns locatedadjacently to both sides of a recording track, which are formed on afull surface of the magnetic recording medium. In the Japanese PatentLaid-Open No. 2000-19200, pre-formatting using a photolithographyprocess and a thin film forming process is only disclosed, and specificservo pattern forming method is not taught. However, by a method similarto the patterned medium forming method of the first embodiment, a servopattern used for the continuous servo system can be formed.

[0146]FIG. 8 shows an example of a servo pattern formed in a medium ofsuch a continuous servo system. As shown in FIG. 8, servo patterns 81are periodically disposed in both sides of each recording track 82 wherea recording region is formed, the patterns being shifted by a halfperiod. A shape of the servo pattern 81 is not limited to a dot shown inthe drawing, but may be a rectangular or long-axis pattern.

[0147] The dot patterns 81 regularly disposed in both sides of therecording track 82 can be patterned by using regular dot resist patternsformed by utilizing the above-described self-organization phenomenon(phase separation phenomenon) of the diblock copolymer. In such a case,since extremely fine patterns can be formed all at once on a fullsurface of the recording medium without using EB writing or the like, itis possible to greatly simplify the process, facilitating the formationof the magnetic recording medium of the continuous servo system.

[0148] There is no particular limitation on the recording system andstructure of the recording layer of the recording medium of the thirdembodiment. A recording layer of a normal longitudinal recording system,or a recoding layer of a perpendicular recording system may be employed.In addition, a continuous film of a single layer, an multilayer filmor apatterned medium as described in each of the first and secondembodiments may be employed. When a patterned medium is formed, writingof servo information can be carried out simultaneously with theformation of the patterned medium.

[0149] Hereinafter, description will be made for examples of the thirdembodiment, which are made by the inventors.

[0150] (Example 7)

[0151] A sample was prepared under conditions similar to those of theexample 2, except for formation of a resist pattern equivalent to thewedge-shaped opening pattern 65 shown in FIG. 7A. That is. CoPt wasdeposited by 20 nm on a Si substrate by a sputtering method. Then,resist was coated in a thickness of about 1.0 μm on the CoPt film byspin coating, and through batch exposure and development, a wedge-shapedopening pattern shown in FIG. 7A was formed. Subsequently, a surface ofthe sample was exposed in F radicals for about 30 seconds while beingmaintained at room temperature. Then, the resist was removed by using anoxygen ashing apparatus.

[0152] By XPS, it was verified that only CoPt of the opening portion ofthe resist exposed to the F radicals was chemically changed to anantiferromagnetic material (CoF₂). Also, when observation was made byMFM, a magnetic image of a wedge-shaped pattern equivalent to a resistpattern was obtained.

[0153] As a result, it was verified that by using the magnetic materialpatterning method of the third embodiment, it was possible to writeservo information, i.e., tracking servo information in a large area allat once.

[0154] (Example 8)

[0155] A sample having the servo pattern 81, shown in FIG. 8, changed toa rectangular shape was prepared. The sample was prepared underconditions similar to those of the example 2, except for formation of anopening pattern corresponding to the servo pattern by using resist. Thatis, CoPt was deposited by 20 nm on a Si substrate by a sputteringmethod. Then, resist was coated in a thickness of about 1.0 μm on theCoPt film by spin coating, and through batch exposure and development, arectangular opening pattern was formed. Subsequently, a surface of thesample was exposed in F radicals for about 30 seconds, while beingmaintained at room temperature. Then, the resist was removed by using anoxygen ashing apparatus.

[0156] By XPS, it was verified that only CoPt of the opening portion ofthe resist exposed to the F radicals was chemically changed to CoF₂.Also, when observation was made by MFM, a magnetic image of arectangular pattern equivalent to the resist pattern was obtained.

[0157] As a result, is was verified that by using the magnetic materialpatterning method of the third embodiment, it was possible to writeservo information, i.e., tracking servo information in a large area allat once.

[0158] [Fourth Embodiment]

[0159] A fourth embodiment relates to a structure of a magneticrecording medium of a deep layer servo system, and a manufacturingmethod thereof.

[0160]FIG. 9 shows the structure of the magnetic recording medium thatis the deep layer servo system of the fourth embodiment.

[0161] A ferromagnetic material layer 64 is formed on a substrate 15,and a nonferromagnetic material region 62 having a servo informationpattern is formed on a surface layer of the ferromagnetic material layer64. A servo layer 60 is composed of the ferromagnetic material layer 64and the nonferromagnetic material region 62. On the servo layer 60, aferromagnetic material layer 25 as a recording layer is formed with anonmagnetic material layer 70 interposed therebetween.

[0162]FIGS. 10A to 10E are process views showing the manufacturingmethod of the magnetic recording medium of the fourth embodiment.

[0163] A servo layer is basically formed by using the same chemicalmethod as that for the fabrication method of the patterned medium of thefirst embodiment. That is, first, as shown in FIG. 10A, theferromagnetic material layer 64 is formed on the substrate 15 by using asputtering method or the like. For this ferromagnetic material layer 64,various ferromagnetic materials containing Co, Ni, Fe can be usedsimilarly to the case of the ferromagnetic material layer 20 of thefirst embodiment. Also, a multilayer film as described above in thesecond embodiment may be formed.

[0164] Then, a resist film is coated on the ferromagnetic material layer64, and through batch exposure and development, on the ferromagneticmaterial layer 64, a resist pattern 32 equivalent to servo informationis formed on a full surface of the substrate. There is no particularlimitation placed on the resist pattern 32, and for example, a generalservo information pattern as shown in FIG. 7A or FIG. 7B may be used.Then, under conditions similar to those of the first embodiment, asurface of the substrate is exposed to active reaction gas or reactionliquid, for example F radicals.

[0165] As shown in FIG. 10B, the ferromagnetic material layer 64 of aregion exposed to the F radicals loses magnetism to be changed to anonferromagnetic material region 62. The nonferromagnetic materialregion 62 needs not be so deep as long as a magnetic pattern as servoinformation can be formed.

[0166] As shown in FIG. 10C, after the remaining resist is removed, anonmagnetic layer 70 is formed on the substrate surface by using a CVDmethod or the like as shown in FIG. 10D. For this nonmagnetic layer 70,an oxide such as SiO₂, Al₂O₃ or TiO₂, a nitride such as Si₃N₄, AlN, TiNor BN, or carbide such as TiC may be used.

[0167] Further, as shown in FIG. 10E, a ferromagnetic material layer 25is formed on the nonmagnetic layer 70. There is no particular limitationplaced on a material and a structure of this ferromagnetic materiallayer 25. A continuous single layer may be used or a patterned medium asdescribed in the first embodiment may be formed. Alternatively, anmultilayer filmas described in the second embodiment may be formed. Inaddition, the ferromagnetic material layer 25 may be set as a recordinglayer of a normal longitudinal recording system or as a recording layerof a perpendicular recording system. Thus, the magnetic recording mediumwith the deep layer servo system is obtained.

[0168] In the magnetic recording medium with the deep layer servosystem, since servo information is written in the servo layer 60independent of the recording layer 25, the servo information can bewritten on a full surface of the servo layer 60. Accordingly,positioning control can be carried out with high accuracy. On the otherhand, the quantity of servo information to be written is greatlyincreased. However, by using the manufacturing method of theabove-described fourth embodiment, since servo information can bewritten all at once, it is possible to greatly shorten the manufacturingprocess.

[0169] Hereinafter, description will be made for examples of the fourthembodiment, which are made by the inventors.

[0170] (Example 9)

[0171] A deep layer servo region was formed by using a method similar tothat of the example 7. That is, CoPt was deposited by about 20 nm on asubstrate by a sputtering method. Then, a resist film was coated in athickness of about 1.0 μm on the CoPt film, and through batch exposureand development, an opening pattern equivalent to the wedge-shaped servopattern shown in FIG. 7A was formed in the resist film. Subsequently, asurface of the sample was exposed in F radicals for about 30 secondswhile being maintained at room temperature. Then, the resist was removedby using an oxygen ashing apparatus.

[0172] Then, SiO2 was deposited by 500 nm on the servo layer by asputtering method, and CoPt to be a recording layer was furtherdeposited by 50 nm by a sputtering method. Accordingly, a magneticrecording medium having a deep layer servo structure was obtained.

[0173] [Fifth Embodiment]

[0174] A fifth embodiment relates to a magnetic recording device (HDD:hard disk drive) equipped with the magnetic recording medium of one ofthe above-described first to fourth embodiments.

[0175]FIG. 11 is a perspective view showing an example of a structure ofa HDD according to the fifth embodiment. As shown in FIG. 11, a magneticrecording medium 100 is mounted on a spindle 101, and rotated by anot-shown motor. An actuator arm 102 attached to a fixed shaft 103 has asuspension 104 in its tip, and a head slider 105 is provided in a tip ofthis suspension 104.

[0176] In a base end of the actuator arm 102, a voice coil motor 106 asa type of a linear motor is provided. This voice coil motor 106 includesa magnetic circuit which is composed of a not-shown driving coil woundup on a bobbin portion of the actuator arm 102, and a permanent magnetand an opposite yoke which are disposed oppositely so as to each otherto sandwich the coil.

[0177] A not-shown recording/reproducing head is formed in a tip of thehead slider 105. By rotation of a disk, the head slider 105 is floatedby keeping a fixed distance with the magnetic recording medium 100, andthe recording/reproducing head is moved relatively to the magneticrecording medium 100. In recording, information is recorded in themagnetic recording medium 100 by a magnetic field generated from therecording head. In reproducing information, by scanning of thereproducing head on the magnetic recording medium, information isreproduced by a leakage magnetic field from each bit on the magneticrecording medium.

[0178]FIG. 12 is a perspective view showing a structure of another HDDof the embodiment. In the case of the above-described HDD shown in FIG.11, the magnetic recording medium is rotated, and recording/reproducingis carried out by the floating type magnetic head. However, when arecording density of the magnetic recording medium becomes much higher,an influence of shaft vibration along with the rotation of the recordingmedium cannot be ignored. On the other hand, in the case of the HDDshown in FIG. 12, no shaft vibration problem occurs because rotarydriving is not used.

[0179] A magnetic recording medium 202 is loaded on a stage 203 whichcan be driven in X, Y and Z directions. A head portion 201 including aplurality of magnetic heads is disposed- oppositely to the magneticrecording medium. The head portion 201 is fixed, and the magneticrecording medium 202 is moved relatively to the head portion 201 bydriving of the stage 203 using a piezo element. Since no rotary-drivingis carried out, the magnetic recording medium needs not be disk-shaped,and a rectangular-shape one or the like can be used as shown in thedrawing.

[0180] The head portion 201 includes the plurality of heads disposed ina multi-array form, and by simultaneously recording/reproducing aplurality of information, it is possible to execute high-speed andlarge-capacity data recording/reproducing. No particular limitation isplaced on the number of heads.

[0181] There is no particular limitation on a method of recordinginformation in the magnetic recording medium. A method of writing by aleakage magnetic field from the head, a method of writing by a magneticfield formed by a current flowing due to charge injection by aneedle-shaped probe, and the like may be used.

[0182] There is also no particular limitation on a method of reproducinginformation of the magnetic recording medium. A method of detecting aleakage magnetic field of the magnetic recording medium, a method ofdetecting spinning of a tunnel current of the recording medium, and thelike may be used.

[0183] If the above-described HDD is equipped with the patterned mediumof the first or the second embodiment, a device which is high in a SNratio, large in capacity and low in manufacturing costs can be provided.Moreover, if the HDD is equipped with the magnetic recording medium ofthe third or the fourth embodiment, manufacturing costs can be reducedby shortening the time of writing servo information. Especially, if themagnetic recording medium of the deep layer servo system of the fourthembodiment is used, a large storage capacity and highly accuratepositioning control can be provided.

[0184] [Sixth Embodiment]

[0185] A sixth embodiment relates to patterning of a magnetic materialother than a magnetic recording medium, especially to patterning of amagnetic random access memory (MRAM).

[0186] The magnetic material patterning method of each of theabove-described first to fourth embodiments can be used for fabricatingvarious magnetic products which require patterning of magnetic materialsother than the magnetic recording medium, the products being, forexample, an MRAM, a motor, a magnetic sensor, a magnetic switch and thelike. Conventionally, in the manufacturing methods of these magneticproducts, physical etching such as ion milling has mainly been used forfabricating a hard magnetic material layer. If a method of changing anunnecessary magnetic material region to a nonmagnetic material by usinghalogenation reaction is used instead, property deterioration of themagnetic material layer, caused by physical damage, can be prevented.

[0187] Especially, in the manufacturing method of the MRAM whereintegration and mass production are required, an advantage obtained byapplying the magnetic material patterning method of each of the first tofourth embodiments is large. The MRAM is one obtained by applying atechnology of magnetic tunnel junction to a random access memory, andhas a magnetic tunnel junction element structure composed of twoferromagnetic material layers and a thin insulating layer sandwitchedtherebetween. Compared with a conventional DRAM, the MRAM is moreadvantageous in that the MRAM can be used as a nonvolatile memory andhas a high access speed. High integration is necessary for securing alarge memory capacity, and in a manufacturing process thereof,microfabrication and simplification of the process are required.

[0188]FIGS. 13A to 13C show an MRAM patterning process of the sixthembodiment. Here, only one memory element is shown; however, in anactual product, similar memory elements are arrayed on the samesubstrate in a matrix form.

[0189] First, as shown in FIG. 13A, on a Si substrate 310 having, forexample, a thermal oxide film formed thereon, a buffer layer 320, alower ferromagnetic material layer 330, a tunnel oxide layer 340, and anupper ferromagnetic material layer 350 are sequentially laminated. Apattern of resist 360 is further formed on the laminated surface. Aplurality of buffer layers and an electrode layer may be providedbetween the Si substrate 310 and the lower ferromagnetic material layer320. In addition, for the lower and upper ferromagnetic material layers330 and 350, as described in the first embodiment, various ferromagneticmaterials containing any of elements Fe, Ni and Co, in composition, canbe used.

[0190] A surface layer is exposed in active reaction gas containinghalogen gas such as fluorine radicals under conditions similar to thoseof the first embodiment. Then, the remaining resist is removed by oxygenashing. As shown in FIG. 13B, a region not covered with a mask of theresist 360 is halogenated from the upper ferromagnetic material layer350 to the lower ferromagnetic material layer 330, and then changed to ahalide 370 as a nonferromagnetic insulating layer.

[0191] Then, by using a normal semiconductor process to form a patternof an upper electrode layer 380 on a recording region layer, a MRAMstructure shown in FIG. 13C is obtained.

[0192] By using the patterning method of the sixth embodiment, it ispossible to separate the respective memory element regions including theupper ferromagnetic material layer 350, the tunnel oxide layer 340 andthe lower electrode layer 330 by a chemical method without etching step.

[0193] If fabrication is carried out by physical etching using theconventional ion milling method, depending on an incident angle of Arions, short-circuiting often occurs in the side wall of the upperferromagnetic material layer 350, the tunnel oxide layer 340 and thelower electrode layer 330 constituting junction. Because there arearticles reattached on a surface by milling. However, by using themagnetic material patterning method of the sixth embodiment, not onlydamage caused by the physical etching, but also short-circuiting or thelike between the upper and lower ferromagnetic material layers 330 and350, caused by residuals after the etching, can be prevented.

[0194] In addition, since the halogenation reaction is used, resistwhich can be subjected to oxygen ashing can be used. If aself-organization resist such as a diblock copolymer is used as theresist, fine patterns can be formed in a large area all at once. Thus,higher integration can be achieved more easily.

[0195] Also, magnetic tunnel junction which can be applied to areproducing magnetic head or the like can be provided by using a similarmagnetic material patterning method.

[0196] Hereinafter, description will be made for an example of the sixthembodiment, which is made by the inventors.

[0197] (Example 10)

[0198] Referring again to FIGS. 13A to 13C, description will be made fora magnetic material patterning method of an example 10 of the sixthembodiment.

[0199] First, as a buffer layer 320, an NiFe film was formed in athickness of about 20 nm on a Si substrate 310 having a thermal oxidefilm by a sputtering method. Subsequently, on the buffer layer 320, a Cofilm having a thickness of about 4 nm as a lower ferromagnetic materiallayer 330, Al₂O₃ having a thickness of about 1 nm as a tunnel oxidelayer, and a Co film having a thickness of about 10 nm as an upperferromagnetic material layer 350 were sequentially laminated. Then,resist was coated in a thickness of about 1 μm on a surface of the upperferromagnetic material layer 350 by spin coating, and through batchexposure and development, a square resist mask pattern of 5.0 μm×5.0 μmwas formed.

[0200] By using an ICP apparatus, the substrate was exposed in generatedF radicals for about 3 minutes. An exposed region not covered with theresist mask was analyzed by using AES, and presence of CoF₂ wasverified. As a result of measuring a change with passage of time in apeak-of CoF₂ while sputtering, presence of CoF₂ up to a depth of 15 nmfrom the surface was verified. In other words, conversion of alljunction portions (Co:4 nm/Al₂O₃:1 nm/Co:10 nm) into halides wasverified.

[0201] Subsequently, the resist was removed by O2 ashing, and then a Cufilm was formed in a thickness of about 300 nm as an upper electrodelayer 380. For patterning, a metal mask was used.

[0202] In order to investigate whether or not short-circuiting occurs inthe side face of junction, resistance values before and afterfabrication were measured. When values standardizing the respectiveresistance values with a junction portion area were R₀ and R₁, R₁/R₀=1was established. Based on the above result, occurrence of noshort-circuiting was verified. In addition, the prepared sample showed R(resistance value)=1.7×10⁶Ω, and MR=10%.

[0203] The MRAM fabricated in the above-described manner exhibited aresistance value and an MR ratio approximately equal to those of theMRAM fabricated by the normal ion milling, indicating that the magneticmaterial patterning method of the sixth embodiment was also effective asthe MRAM fabrication method.

[0204] The description has been hereinbefore made for the magneticrecording medium and its manufacturing method of the present inventionaccording to the respective embodiments. However, it should beunderstood that the present invention is not limited to the embodimentsdescribed above. Modifications and variations of the embodimentsdescribed above will occur to those skilled in the art, in light of theabove teaching.

1. A method of patterning magnetic material comprising: (a) preparing aferromagnetic material layer containing at least one element selectedfrom the group consisting of Fe, Co and Ni; (b) masking a surface of theferromagnetic material layer selectively; and (c) makingnonferromagnetic comprising: exposing an exposed portion of the surfaceof the ferromagnetic material layer in halogen-containing activereaction gas or reaction liquid, converting the exposed portion and alower layer thereof into a compound with a component in the reaction gasor the reaction liquid by chemical reaction; and making the compoundnonferromagnetic.
 2. The method of claim 1, wherein the halogen isfluorine.
 3. The method of claim 1, wherein the compound is a cobaltfluoride.
 4. The method of claim 1, wherein the halogen-containingactive reaction gas is generated by a plasma generating apparatus. 5.The method of claim 1, wherein the masking and the makingnonferromagnetic steps write servo information for controlling at leastone of a position and a speed on the ferromagnetic material layer, theposition and the speed are relative to a magnetic head.
 6. The method ofclaim 1, wherein the masking step comprises: forming a block copolymerlayer composed of a plurality of island regions and a separation regionthat separate the island regions from each other, on the surface of theferromagnetic material layer by a self-organization phenomenon; andremoving the island regions selectively.
 7. The method of claim 6,wherein the making nonferromagnetic step forms magnetic recordingregions corresponding to the island regions and a nonferromagneticregion corresponding to the separation region, and the separation regionis removed after the making nonferromagnetic step.
 8. The method ofclaim 7, wherein servo information for controlling at least one of aposition and a speed is written in each of the magnetic recordingregions, the position and the speed are relative to a magnetic head.9-18 (Cancelled).